JP2001133685A - Photographic lens, electronic still camera, and video camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photographic lens system where the resolution of an entire image is high in a wide range of the object distance and the overall optical length is short. SOLUTION: This photographic lens system is provided with a first lens group having a negative power, a second lens group having a positive power, a third lens group having a positive power, a fourth lens group having a positive power, and a stop arranged between the second and third lens groups in order from the object side. The first lens group is provided with a negative meniscus lens as a first lens, of which the face having a high curvature is directed to the image side and a negative lens as a second lens, and the second lens group is provided with a double convex lens as a third lens, and the third lens group is provided with a positive lens as a fourth lens, a double concave lens as a fifth lens, and a positive lens as a sixth lens of which the face having a high curvature is directed to the image side, and the fourth lens group is provided with a positive lens as a seventh lens, and at least the face on the image side of the sixth lens is aspherical. By this constitution, the photographic lens system is provided where the resolution of an entire image is high in a wide range of the object distance and the overall optical length is short.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high quality image pickup lens used for an electronic still camera, a video camera and the like.

[0002]

2. Description of the Related Art With the progress and spread of personal computers, electronic still cameras are rapidly spreading. The total number of pixels of the solid-state image sensor used in electronic still cameras is
An electronic still camera equipped with a solid-state image sensor having more than 1 million pixels and more than 2 million pixels in total has recently been commercialized. Video cameras are also equipped with functions that can capture high-quality still images in addition to moving images.

When the number of pixels of a solid-state image sensor increases in an imaging lens used in an electronic still camera or a video camera, the following points must be noted.

It is necessary to improve the resolution of an imaging lens in response to the increase in the number of pixels of a solid-state imaging device.

[0005] In the solid-state imaging device, when the number of pixels is increased while the screen size remains the same, the pixel pitch is reduced, the aperture ratio is reduced, and the light receiving sensitivity is reduced. Therefore, a minute positive lens is provided for each pixel of the solid-state imaging device to increase the effective aperture ratio, thereby preventing a decrease in light receiving sensitivity. In this case, the imaging lens needs to make the principal ray incident on each pixel parallel to the optical axis, that is, telecentric, so that most of the light emitted from each minute positive lens reaches the light receiving area of the corresponding pixel. is there. The smaller the pixel pitch, the better the telecentricity needs to be.

Further, an infrared cut filter, an optical low-pass filter, a cover glass of the solid-state image sensor, and an air gap between the cover glass and the light-receiving surface are arranged between the imaging lens and the light receiving surface of the solid-state image sensor. Therefore, the imaging lens needs to have a longer back focus.

For electronic still cameras and video cameras, there is a demand for a compact camera body.
It is necessary to shorten the entire optical length of the imaging lens (the distance from the object-side tip of the imaging lens to the light receiving surface of the solid-state imaging device).

As a fixed focus image pickup lens used in an electronic still camera, a retro focus type fixed focus lens having good telecentricity is used (for example, Japanese Patent Application Laid-Open Nos. H11-23961 and H11-24).
No. 9009). These imaging lenses are configured to perform focus adjustment by moving one positive lens or a lens group closer to the image than the stop in the optical axis direction for automatic focus adjustment.

[0009]

As described above, as the number of pixels of the solid-state imaging device increases, it is necessary to increase the resolution of the imaging lens. For that purpose, it is necessary to reduce various aberrations. It is necessary to reduce various aberrations such as spherical aberration and astigmatism as compared with the imaging lens disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 11-23961.

The normal shooting distance of an electronic still camera is ∞ to
In many cases, the resolution is set to 0.5 m. With the conventional imaging lens, when the shooting distance is 画面, the resolution is good over the entire screen, but when the shooting distance is 0.5 m, the resolution at the center of the screen is Although high, there is a problem that the resolution at the periphery of the screen is low. The shooting distance is 0.2m in macro mode.
Although it is possible to take a picture even at a short distance, there is a problem that the resolution is extremely low in the periphery of the screen even though the resolution at the center of the screen is good.

SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging lens having a high resolution over a wide range of photographing distance and a short overall optical length.

[0012]

In order to achieve the above object, an imaging lens according to the present invention is configured as follows.

The first imaging lens of the present invention comprises, in order from the object side, a first lens unit having a negative power, a second lens unit having a positive power, a third lens unit having a positive power, and a fourth lens unit having a positive power. A negative meniscus lens comprising: a lens group; and a stop disposed between the second lens group and the third lens group, wherein the first lens group has a surface having a strong curvature directed in order from the object side to the image side. The second lens group includes a biconvex lens, and the third lens group includes, in order from the object side, a positive lens, a biconcave lens, and a positive lens having a surface with a strong curvature facing the image side. The fourth lens group includes a positive lens, at least the most image-side surface of the third lens group is an aspheric surface, and when the shooting distance is ∞, the combined focal length of the entire lens system is f, The composite focal length of the first lens group is f _G1 , and the composite focal length of the second lens group is f _G1 . Point distance f _G2, a composite focal length of the third lens group as f _G3, the composite focal length of the fourth lens group _{f G4, 0.8 <| f G1} | / f <1.2 ‥‥‥ _{(1) 1.3 <f G2 /f<2.4} ‥‥‥ (2) 1.2 <f G3 /f<2.3 ‥‥‥ (3) 1.6 <f G4 / f <2. 6 ‥‥‥ (4).

[0014] In the first imaging lens, further,
Assuming that the refractive index of the lens closest to the object side of the third lens group is n _A and the radius of curvature of the object side surface of the lens is r _A , 0.9 <r _A / f (n _A −1) <1.8. It is desirable to configure so as to satisfy the condition of ‥‥‥ (5).

It is preferable that the most object side surface of the third lens group is also aspherical.

[0016] Of the at least three lenses constituting the third lens group, two lenses on the image side may be cemented. The fourth lens group may be a combination of a positive lens and a negative lens.

In a state where a predetermined parallel plate element is arranged between the fourth lens group and the image plane, the air gap between the third lens group and the fourth lens group is from the stop to the image plane. It is preferable to maximize the air gap existing between the air gaps.

The second imaging lens according to the present invention comprises, in order from the object side, a first lens unit having a negative power, a second lens unit having a positive power, a third lens unit having a positive power, and a fourth lens unit having a positive power. A lens group, and a diaphragm disposed between the second lens group and the third lens group, wherein focus adjustment is performed by moving the first lens group along an optical axis. It is.

In the second imaging lens, the first lens
Group is a negative lens with the surface with strong curvature facing the image side in order from the object side
A second lens group including a varnish lens and a negative lens;
The third lens group includes a biconvex lens.
Lens, a biconcave lens, and a lens with a strong curvature facing the image side.
The fourth lens group includes a positive lens,
At least the image-side surface of the third lens group is an aspheric surface.
And the combined focal length of the entire lens system when the shooting distance is ∞
And f is the composite focal length of the first lens group._G1The said
Let the composite focal length of the two lens groups be f_G2, Of the third lens group
Let the composite focal length be f _G3, The combined focal length of the fourth lens group
To f_G40.8 <| f_G1| / F <1.2 ‥‥‥ (1) 1.3 <f_G2/F<2.4‥‥‥(2) 1.2 <f_G3/F<2.3‥‥‥(3) 1.6 <f_G4/F<2.6‥‥‥(4)

Further, assuming that the refractive index of the lens closest to the object side of the third lens group is n _A , and the radius of curvature of the object side surface of the lens is r _A , 0.9 <r _A / f (n _A- 1) <1.8 It is desirable to satisfy the condition of ‥‥‥ (5).

It is preferable that the most object side surface of the third lens group is also aspherical.

The two lenses on the image side among at least three lenses constituting the third lens group may be cemented. The fourth lens group may be a combination of a positive lens and a negative lens.

With a predetermined parallel plate element disposed between the fourth lens group and the image plane, the air gap between the third lens group and the fourth lens group is from the stop to the image plane. It is preferable to maximize the air gap existing between the air gaps.

A first electronic still camera and a first video camera according to the present invention each include a solid-state image sensor and an imaging lens, and use the first imaging lens as the imaging lens.

A second electronic still camera and a second video camera according to the present invention include a solid-state image pickup device and an image pickup lens, and use the second image pickup lens as the image pickup lens.

In each of the first and second electronic still cameras and the first and second video cameras, a solid-state imaging device having a minute positive lens for each pixel can be used.

In the second electronic still camera and the second video camera, the space between the most image-side lens of the imaging lens and the light-receiving surface of the solid-state imaging device may have a sealed structure. Further, a transparent plate having a parallel plane may be arranged on the object side of the imaging lens.

The above-mentioned conditional expression will be described.

Conditional expression (1) is a condition for restricting the negative power of the first lens group G1, thereby correcting various aberrations of the entire lens system in a well-balanced manner, and shortening the overall optical length as much as possible. When | f _G1 | / f exceeds the upper limit of 1.2, the radius of curvature of the concave surface included in the first lens group G1 increases, so that the Petzval sum of the entire lens system does not decrease and the field curvature decreases. This makes it difficult to improve the resolution on the light receiving surface of the solid-state imaging device over the entire screen. In addition, since the negative power of the first lens group G1 is weak, if a predetermined back focus is to be obtained, the air gap between the first lens group G1 and the second lens G2 must be increased, and the total optical length Is difficult to shorten. On the other hand, when | f _G1 | / f exceeds the lower limit of 0.8, the Petzval sum decreases because the radius of curvature of the concave surface included in the first lens group G1 decreases, but the frame generated in the first lens group G1 decreases. Aberration and astigmatism become excessive, and it becomes difficult to correct these aberrations in the second lens group G2 and thereafter.

Conditional expression (2) is a condition for correcting various aberrations of the entire lens system in a well-balanced manner in combination with conditional expression (1). If f _G2 / f exceeds the upper limit of 2.4, the third lens group G3 excessively bears the positive power required for the lens system composed of the second lens group G2 and the third lens group G3. And various aberrations generated by the first lens group G1 and the second lens G2 are reduced by the third lens group G3 and the fourth lens group G.
4 makes it difficult to correct. On the other hand, if f _G2 / f exceeds the lower limit of 1.3, the second lens group G2 generates positive distortion, so that the distortion of the entire lens system can be reduced, but the Petzval sum cannot be reduced. Therefore, it is difficult to satisfactorily correct the field curvature.

Conditional expression (3) is a condition for correcting various aberrations of the entire lens system with good balance in combination with conditional expressions (1) and (2). If f _G3 / f exceeds the upper limit of 2.3, the second lens group G2 and the third lens group G
Since the positive power required for the lens system composed of the lens unit 3 and the lens unit 3 is insufficient, the air gap between the first lens unit G1 and the second lens unit G2 is increased, and the overall optical length is increased. . On the other hand, when f _G3 / f exceeds the lower limit of 1.2, the third
Since the lens group G3 generates excessive negative distortion, it is difficult to reduce the distortion of the entire lens system even if the lens surface of the third lens group G3 closest to the image side is aspheric. .

Conditional expression (4) is a condition for improving telecentricity. If f _G4 / f exceeds the upper limit of 2.6, the positive power of the fourth lens group G4 is insufficient, so that it is difficult to improve the telecentricity. In this case, the telecentricity can be corrected by increasing the air gap between the third lens group G3 and the fourth lens group G4, but this increases the total optical length. On the other hand, if f _G4 / f exceeds the lower limit of 1.6, the telecentricity can be improved, but the fourth lens group G4 generates excessive negative distortion. Therefore, it is necessary to reduce the distortion of the entire lens system. Becomes difficult.

Conditional expression (5) is a condition for reducing the field curvature and shortening the total optical length. R _A / f (n _A -1) in the conditional expression (5) is a ratio of the focal length of the surface of the third lens group G3 closest to the stop to the focal length f of the entire lens system. If r _A / f (n _A -1) exceeds the upper limit of 1.8, the principal point of the third lens group G3 will be closer to the image side.
If an attempt is made to improve the telecentricity, the air gap between the third lens group G3 and the fourth lens group G4 will be increased, and the overall optical length will be increased. If the total optical length is forcibly shortened, the positive power of the second lens group G2 or the third lens group G3 is increased, so that the Petzval sum cannot be reduced and the curvature of field is favorably corrected. Becomes difficult. Also, the first lens group G1
And the coma generated by the second lens group G2 cannot be corrected completely by the third lens group G3 and the fourth lens group G4. On the other hand, if r _A / f (n _A −1) exceeds the lower limit of 0.9, the third
The two principal points of the lens group G3 approach the stop, and the back focus of the third lens group G3 is shortened. Therefore, even if the telecentricity is improved, the length from the stop to the image plane can be shortened, and the entire optical length is obtained. Can be shortened,
Since the Petzval sum becomes large, it becomes difficult to satisfactorily correct the field curvature.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings and tables.

(Embodiment 1) FIG. 1 shows a configuration of an imaging lens according to Embodiment 1 of the present invention.

The first lens 11 is composed of seven lenses.
And the second lens 12 are each a negative meniscus lens having a surface with a strong curvature facing the image side, the third lens 13 is a biconvex lens, the fourth lens 14 is a biconvex lens having an aspheric object side surface, and the fifth lens. Reference numeral 15 denotes a biconcave lens, sixth lens 16 denotes a biconvex lens having an aspherical surface on the image side, and seventh lens 17 denotes a biconvex lens. A stop 18 is arranged between the third lens 13 and the fourth lens 14.

The first lens 11 and the second lens 12
The lens group G1 is configured, the third lens 13 configures a second lens group G2, the fourth lens 4, the fifth lens 15, and the sixth lens 16 configure a third lens group G3.
The lens 17 forms the fourth lens group G4.

A filter combining an infrared cut filter and an optical low-pass filter is arranged on the image side of the fourth lens group G4, and an image pickup device is arranged on the image side. The solid-state imaging device is provided with a cover glass on the object side of the imaging surface. In FIG. 1, the filter and the cover glass are represented by one equivalent parallel flat plate element F, and the light receiving surface of the solid-state imaging device is denoted by P.
It is represented by

Table 1 shows lens data when the imaging distance of the imaging lens shown in FIG. All units of length in the table are mm. i is a surface number sequentially assigned from the object side,
j is a lens number given in order from the object side, Lj is a j-th lens, A is a diaphragm, F is an equivalent parallel plate element, and P is a light receiving surface of a fixed image sensor. r _i is the radius of curvature of the i-th surface, and d _i is the i-th surface
The distance from one surface to the next surface, n _j and ν _j are the refractive index at the d-line of the j-th lens and the Abbe number, and n _F and ν _F are the refractive index and the Abbe number at the d-line of the equivalent parallel plate element F, respectively. It is. The surface marked with * is an aspherical surface, and the aspherical shape is defined by the following equation.

[0040]

(Equation 1)

Where κ _i is the conic constant of the ith surface, D _i , E
_i , F _i , and G _i are the fourth, sixth, eighth, and first orders of the i-th surface, respectively.
A zero-order aspherical coefficient, h is a height from the optical axis, and S is a sag amount at a height h on the i-th surface on the aspherical surface.

[0042]

[Table 1]

F is the combined focal length of the entire lens system, F _NO is the aperture ratio when the shooting distance is ∞, L is the total optical length when the shooting distance is ∞, D is the diameter of the effective image circle, and f _G1 is The composite focal length of one lens group, f _G2 is the composite focal length of the second lens group,
f _G3 is the combined focal length of the third lens group, and f _G4 is the combined focal length of the fourth lens group.

The operation of the imaging lens shown in FIG. 1 will be described.

The imaging lens according to the present invention employs a retrofocus lens which is advantageous for widening the angle in order to increase the angle of view on the object side, and uses an image side of the retrofocus lens which improves the telecentricity. Has a positive lens. That is, since the first lens group G1 has negative power and the lens system obtained by combining the second lens group G2 and the third lens group G3 has positive power, the first lens group G1 to the third lens group G3 A retrofocus type lens is constituted by the lens system described above. The fourth lens group G4 is a lens for improving telecentricity.

In the space between the fourth lens group G4 and the image plane, a space for disposing the infrared cut filter, the optical low-pass filter, and the cover glass of the image sensor can be secured. The air gap between the third lens group G3 and the fourth lens group G4 is set to be the largest among the air gaps existing from the stop to the image plane. In order to shorten the overall optical length of the imaging lens, it is good to shorten the air spacing of each part,
In consideration of improving the telecentricity, it is advantageous to increase only the air gap between the third lens group G3 and the fourth lens group G4.

The retrofocus type lens is apt to generate negative distortion, and the fourth lens group G4 is also apt to generate negative distortion. However, the first lens group G1 is composed of two negative lenses. By making the most image-side surface of the three lens group G3 aspherical, negative distortion of the entire lens system is reduced. In addition, by making the most object side surface of the third lens group G3 aspherical, spherical aberration of the entire lens system is favorably corrected.

The focus adjustment when the photographing distance is changed is performed by fixing the lenses from the second lens group G2 to the image pickup device and moving only the first lens group G1 in the optical axis direction. As the shooting distance becomes shorter, the first lens group G1 moves toward the object side. In the entire range or most range of the predetermined photographing distance, when the photographing distance changes, both the spherical aberration and the astigmatism change in the same direction, and the degree of the change is the same.

The first lens group G1 is composed of two lenses and has a light moving part including other moving mechanical parts, so that it can be moved at a high speed by a motor having a small power. In the method of performing focus adjustment by moving the entire lens system, generally, when the shooting distance changes, the spherical aberration and astigmatism on the image plane change, so that the resolution of the entire screen can be improved over a wide range of the shooting distance. However, in the imaging lens of the present invention, both the spherical aberration and the astigmatism change in the same direction when the shooting distance changes in the entire range or the most range of the predetermined shooting distance. In addition, since the degree of change is the same, the resolution of the entire screen can be improved over a wide range of the photographing distance.

FIGS. 2, 3 and 4 show aberration diagrams of the imaging lens shown in FIG. 1 when the aperture is opened. FIG. 2 shows spherical aberration, astigmatism, and distortion when the shooting distance is Δ, and FIG. 3 shows spherical aberration, astigmatism, and distortion when the shooting distance is 0.5 m.
Are spherical aberration, astigmatism, and distortion when the shooting distance is 0.2 m. W is a half angle of view. It can be seen from FIGS. 2 to 4 that various aberrations are well corrected even when the shooting distance changes. In particular, when the shooting distance is reduced from ∞, the spherical aberration and astigmatism are inclined in the same under direction, and the amount of the inclination is substantially the same, so that the shooting distance is wide in the range of ∞ to 0.2 m. The resolution of the entire screen can be increased.

As a solid-state image sensor, the number of pixels is 1800 × horizontal.
It is possible to use a pixel having a vertical 1200, a pixel pitch of 4.2 μm for both horizontal and vertical, and each pixel arranged in a square.

When the distance (optical total length) from the tip of the first lens unit to the image pickup device when the shooting distance is Δ is L and the diagonal length of the effective area of the solid-state image pickup device is D, L / D is When referred to as the optical total length ratio, the optical total length ratio of the imaging lens shown in FIG. 1 is 2.97.

Although the eccentricity tolerance of the three lenses of the fourth lens 14, the fifth lens 15, and the sixth lens 16 is strict, the fifth lens 15 and the sixth lens 16
An eccentricity error between the lens 15 and the sixth lens 16 can be reduced.

The focus adjustment can also be performed by moving the entire lens system while fixing the air gap between the second lens 12 and the third lens 13 at d ₄ = 2.22 mm. Can obtain an image with a good resolution over the entire screen when the shooting distance is in the range of ∞ to 0.5 m.

(Embodiment 2) FIG. 5 shows a configuration of an imaging lens according to Embodiment 2 of the present invention.

Similar to the image pickup lens shown in FIG. 1, the first lens 21 and the second lens 22 are each composed of seven lenses, and each of the first lens 21 and the second lens 22 is a negative meniscus lens having a surface with a strong curvature facing the image side. The third lens 23 is a biconvex lens, the fourth lens 24 is a biconvex lens having an aspherical surface on the object side, the fifth lens 25 is a biconcave lens, the sixth lens 26 is a biconvex lens having an aspherical surface on the image side, and the seventh lens. 27 is a biconvex lens. The fifth lens 25 and the sixth lens 26 are joined. An aperture 28 is arranged between the third lens 23 and the fourth lens 24.

The first lens group G1 includes the first lens 21 and the second lens
The second lens group G2 includes a third lens 23, and the third lens group G3 includes a fourth lens 2
4, a fifth lens 25 and a sixth lens 26,
The fourth lens group G4 includes a seventh lens 27.
A parallel plate element F equivalent to a filter and a cover glass is arranged on the image side of the fourth lens group G4, and a light receiving surface P of the solid-state imaging device is arranged on the image side.

Table 2 shows lens data when the imaging distance of the imaging lens shown in FIG. The definition of each parameter is the same as in Table 1.

[0059]

[Table 2]

The focus adjustment when the photographing distance is changed is performed by fixing the lenses from the second lens group G2 to the image pickup device and moving only the first lens group G1 in the optical axis direction.

FIGS. 6, 7, and 8 show aberration diagrams of the imaging lens shown in FIG. 5 when the aperture is opened. 6 shows spherical aberration, astigmatism, and distortion when the shooting distance is Δ, and FIG. 7 shows spherical aberration, astigmatism, and distortion when the shooting distance is 0.5 m.
Are spherical aberration, astigmatism, and distortion when the shooting distance is 0.2 m. 6 to 8, it can be seen that various aberrations are well corrected even when the photographing distance changes. In particular,
When the shooting distance decreases from ∞, the spherical aberration and astigmatism tilt in the same under direction, and the amount of tilt is almost the same. Resolution can be increased.

As a solid-state image pickup device, the number of pixels is 1800 × horizontal.
It is possible to use a pixel having a vertical 1200, a pixel pitch of 4.2 μm for both horizontal and vertical, and each pixel arranged in a square.

The fourth lens 24, the fifth lens 25,
Although the eccentricity tolerance of the three lenses of the sixth lens 26 is strict, when the fifth lens 25 and the sixth lens 26 are joined, the fifth lens 2
The eccentric error of the fifth and sixth lenses 26 can be reduced.

The focus adjustment can also be performed by moving the entire lens system while fixing the air gap between the second lens 22 and the third lens 23 at d4 = 2.22 mm. In this case, An image with a good resolution over the entire screen can be obtained when the shooting distance is in the range of 解像度 to 0.5 m.

(Embodiment 3) FIG. 9 shows a configuration of an imaging lens according to Embodiment 3 of the present invention.

As in the case of the imaging lens shown in FIG. 1, the lens is composed of seven lenses, the first lens 31 is a negative meniscus lens having a surface with a strong curvature facing the image side, and the second lens 32 is a surface having a strong curvature. , The third lens 33 is a biconvex lens, the fourth lens 34 is a biconvex lens, and the fifth lens 3
Reference numeral 5 denotes a biconcave lens, a sixth lens 36 denotes a biconvex lens having an aspherical surface on the image side, and a seventh lens 37 denotes a biconvex lens. Third
A stop 38 is arranged between the lens 33 and the fourth lens 34.

The first lens group G1 includes the first lens 31 and the second lens
The second lens group G2 includes a third lens 33, and the third lens group G3 includes a fourth lens 3.
4, a fifth lens 35 and a sixth lens 36,
The fourth lens group G4 includes a seventh lens 37.
The parallel plate element F is arranged on the image side of the fourth lens group G4, and the light receiving surface P of the solid-state imaging device is arranged on the image side.

Table 3 shows lens data when the imaging distance of the imaging lens shown in FIG. 9 is ∞. The definition of each parameter is the same as in Table 1.

[0069]

[Table 3]

The focus adjustment when the photographing distance is changed is performed by fixing the lenses from the second lens group G2 to the image pickup device and moving only the first lens group G1 in the optical axis direction.

FIGS. 10, 11 and 12 show aberration diagrams of the imaging lens shown in FIG. 9 when the aperture is opened. 10 shows a case where the shooting distance is Δ, and FIG. 11 shows a case where the shooting distance is 0.5 m.
Reference numeral 2 denotes spherical aberration, astigmatism, and distortion when the shooting distance is 0.2 m. 10 to 12, it can be seen that various aberrations are satisfactorily corrected even when the shooting distance changes.

As a solid-state image sensor, the number of pixels is 1800 × horizontal.
It is possible to use a pixel having a vertical 1200, a pixel pitch of 4.2 μm for both horizontal and vertical, and each pixel arranged in a square.

It is also possible to adjust the focus by moving the entire lens system while fixing the air gap between the second lens 32 and the third lens 33 at d ₄ = 2.02 mm. Can obtain an image with a good resolution over the entire screen when the shooting distance is in the range of ∞ to 0.5 m.

(Embodiment 4) FIG. 13 shows a configuration of an imaging lens according to Embodiment 4 of the present invention.

The first lens 41 is composed of eight lenses.
And the second lens 42 are each a negative meniscus lens having a surface with a strong curvature facing the image side, the third lens 43 is a biconvex lens, the fourth lens 44 is a biconvex lens having an aspheric object side surface, and the fifth lens. Reference numeral 45 denotes a biconcave lens, a sixth lens 46 denotes a biconvex lens having an aspherical surface on the image side, a seventh lens 47 denotes a biconvex lens, and an eighth lens 48 denotes a negative meniscus lens having a surface with a strong curvature directed to the object side. The seventh lens 47 and the eighth lens 48 are joined. An aperture 49 is arranged between the third lens 43 and the fourth lens 44.

The first lens 41 and the second lens 42
The third lens 43 forms a second lens group G2, the fourth lens 44, the fifth lens 45, and the sixth lens 46 form a third lens group G3. The eighth lens 48 constitutes a fourth lens group G4. On the image side of the fourth lens group G4, a filter and a parallel plate element F equivalent to a cover glass are arranged.
The light receiving surface P of the solid-state imaging device is arranged on the image side.

The fourth lens group G4 is a cemented lens in order to satisfactorily correct lateral chromatic aberration.

The shooting distance of the imaging lens shown in FIG.
Table 4 shows lens data in the case of. The definition of each parameter is the same as in Table 1.

[0079]

[Table 4]

The focus adjustment when the photographing distance is changed is performed by fixing the lens from the second lens group G2 to the image pickup device and moving only the first lens group G1 in the optical axis direction.

FIGS. 14, 15 and 16 show aberration diagrams of the imaging lens shown in FIG. 13 when the aperture is opened. 14 shows a case where the shooting distance is Δ, FIG. 15 shows a case where the shooting distance is 0.5 m, and FIG. 16 shows a case where the shooting distance is 0.2 m.
This is distortion. It can be seen from FIGS. 14 to 16 that various aberrations are well corrected even when the shooting distance changes.

As a solid-state image sensor, the number of pixels is 1800 × horizontal.
It is possible to use a pixel having a vertical 1200, a pixel pitch of 4.2 μm for both horizontal and vertical, and each pixel arranged in a square.

It is also possible to adjust the focus by moving the entire lens system while fixing the air gap between the second lens 42 and the third lens 43 at d ₄ = 2.22 mm. Can obtain an image with a good resolution over the entire screen when the shooting distance is in the range of ∞ to 0.5 m.

(Embodiment 5) FIG. 17 shows a configuration of an imaging lens according to Embodiment 5 of the present invention.

The first lens 51 is composed of seven lenses.
And the second lens 52 are each a negative meniscus lens having a surface with a strong curvature facing the image side, the third lens 53 is a biconvex lens, the fourth lens 54 is a biconvex lens having an aspheric object side surface, and the fifth lens. 55 is a biconcave lens, 6th lens 56 is a biconvex lens whose image side is aspherical, and 7th lens 57 is a biconvex lens. The fifth lens 55 and the sixth lens 56 are joined, and a diaphragm 58 is arranged between the third lens 53 and the fourth lens 54.

The first lens 51 and the second lens 52 form the first
The third lens 53 forms a second lens group G2, the fourth lens 54, the fifth lens 55, and the sixth lens 56 form a third lens group G3, and the seventh lens 57 forms a third lens group G3. The fourth lens group G4 is configured. A parallel plate element F equivalent to a filter and a cover glass is arranged on the image side of the fourth lens group G4, and a light receiving surface P of the solid-state imaging device is arranged on the image side.

The shooting distance of the imaging lens shown in FIG.
Table 5 shows lens data in the case of.

[0088]

[Table 5]

The focus adjustment when the photographing distance is changed is performed by fixing the lenses from the second lens group G2 to the image pickup device and moving only the first lens group G1 in the optical axis direction.

FIG. 1 is an aberration diagram of the imaging lens shown in FIG.
8, FIG. 19 and FIG. FIG. 18 shows spherical aberration, astigmatism, and distortion when the shooting distance is Δ, FIG. 19 shows the case where the shooting distance is 0.5 m, and FIG. 20 shows the case where the shooting distance is 0.2 m. 18 to 20, it can be seen that various aberrations are favorably corrected even when the shooting distance changes.

As the solid-state imaging device, the number of pixels is 1800 × horizontal.
It is possible to use a pixel having a vertical 1200, a pixel pitch of 4.2 μm for both horizontal and vertical, and each pixel arranged in a square.

Note that the focus adjustment can be performed by moving the entire lens system while fixing the air gap between the second lens 52 and the third lens 53 at d ₄ = 2.20 mm. Can obtain an image with a good resolution over the entire screen when the shooting distance is in the range of ∞ to 0.5 m.

(Embodiment 6) FIG. 21 shows the configuration of an imaging lens according to Embodiment 6 of the present invention.

The first lens 61 is composed of seven lenses.
And the second lens 62 are each a negative meniscus lens having a surface with a strong curvature facing the image side, the third lens 63 is a biconvex lens, the fourth lens 64 is a biconvex lens having an aspheric object side surface, and the fifth lens. 65 is a biconcave lens, 6th lens 66 is a biconvex lens whose surface on the image side is aspherical, and 7th lens 67 is a biconvex lens. A stop 68 is arranged between the third lens 63 and the fourth lens 64.

The first lens 61 and the second lens 62
The third lens 63 constitutes a second lens group G2, the fourth lens 64, the fifth lens 65, and the sixth lens 66 constitute a third lens group G3, and the seventh lens 67 constitutes a third lens group G1. The fourth lens group G4 is configured. A parallel plate element F equivalent to a filter and a cover glass is arranged on the image side of the fourth lens group G4, and a light receiving surface P of the solid-state imaging device is arranged on the image side.

The shooting distance of the imaging lens shown in FIG.
Table 6 shows lens data in the case of.

[0097]

[Table 6]

The focus adjustment when the photographing distance is changed is performed by fixing the lens from the second lens group G2 to the image pickup device and moving only the first lens group G1 in the optical axis direction.

FIG. 2 shows aberration diagrams of the imaging lens shown in FIG.
2, FIG. 23 and FIG. 22 shows the spherical aberration, astigmatism, and distortion when the shooting distance is Δ, FIG. 23 shows the case where the shooting distance is 0.5 m, and FIG. 24 shows the case where the shooting distance is 0.2 m. It can be seen from FIGS. 22 to 24 that various aberrations are favorably corrected even when the shooting distance changes.

As a solid-state image sensor, the number of pixels is 1800 × horizontal.
It is possible to use a pixel having a vertical 1200, a pixel pitch of 4.2 μm for both horizontal and vertical, and each pixel arranged in a square.

The focus adjustment can be performed by moving the entire lens system with the air gap between the second lens 62 and the third lens 63 fixed at d ₄ = 2.21 mm. Can obtain an image with a good resolution over the entire screen when the shooting distance is in the range of ∞ to 0.5 m.

(Embodiment 7) FIG. 25 shows a configuration of an imaging lens according to Embodiment 7 of the present invention.

The first lens 71 is composed of seven lenses.
The second lens 72 is a negative meniscus lens having a surface with a strong curvature facing the image side, the third lens 73 is a biconvex lens, the fourth lens 74 is a biconvex lens, the fifth lens 75 is a biconcave lens, and the sixth lens. Reference numeral 76 denotes a biconvex lens having an aspherical surface on the image side, and a seventh lens 77 denotes a positive meniscus lens having a surface with a strong curvature directed to the image side.

The first lens 71 and the second lens 72
The third lens 73 forms a second lens group G2, the fourth lens 74, the fifth lens 75, and the sixth lens 76 form a third lens group G3, and the seventh lens 77 forms a third lens group G3. A fourth lens group G4 is formed, and an aperture 78 is arranged between the third lens group 73 and the fourth lens 74. A parallel plate element F equivalent to a filter and a cover glass is arranged on the image side of the fourth lens group G4, and a light receiving surface P of the solid-state imaging device is arranged on the image side.

The shooting distance of the imaging lens shown in FIG.
Table 7 shows lens data in the case of.

[0106]

[Table 7]

The focus adjustment when the photographing distance is changed is performed by fixing the lens from the second lens group G2 to the image pickup device and moving only the first lens group G1 in the optical axis direction.

FIG. 2 shows aberration diagrams of the imaging lens shown in FIG.
6, FIG. 27 and FIG. 26 shows the spherical aberration, astigmatism, and distortion when the shooting distance is Δ, FIG. 27 shows the case where the shooting distance is 0.5 m, and FIG. 28 shows the case where the shooting distance is 0.2 m. 26 to 28, it can be seen that various aberrations are well corrected even when the shooting distance changes.

As a solid-state image sensor, the number of pixels is 1800 × horizontal.
A vertical 1200 pixel pitch of 3.3 μm for both horizontal and vertical pixels and a square array of pixels can be used.

The focus adjustment can be performed by moving the entire lens system with the air gap between the second lens 72 and the third lens 73 fixed at d ₄ = 1.58 mm. Can obtain an image with a good resolution over the entire screen when the shooting distance is in the range of ∞ to 0.5 m.

(Eighth Embodiment) FIG. 29 shows the structure of an imaging lens according to an eighth embodiment of the present invention.

The first lens 81 is composed of seven lenses.
And the second lens 82 are each a negative meniscus lens having a surface with a strong curvature facing the image side, the third lens 83 is a biconvex lens, the fourth lens 84 is a biconvex lens having an aspheric object side surface, and the fifth lens. 85 is a biconcave lens, 6th lens 86 is a biconvex lens whose image side is aspherical, and 7th lens 87 is a biconvex lens.

The first lens 81 and the second lens 82
A third lens group G1 is formed, a third lens group 83 is formed as a second lens group G2, a fourth lens 84, a fifth lens 85, and a sixth lens 86 are formed as a third lens group G3, and a seventh lens 87 is formed as a third lens group. A fourth lens group G4 is formed, and a stop 88 is arranged between the third lens group 83 and the fourth lens 84. A parallel plate element F equivalent to a filter and a cover glass is arranged on the image side of the fourth lens group G4, and a light receiving surface P of the solid-state imaging device is arranged on the image side.

The shooting distance of the imaging lens shown in FIG.
Table 8 shows lens data in the case of.

[0115]

[Table 8]

The focus adjustment when the photographing distance is changed is performed by fixing the lens from the second lens group G2 to the image pickup device and moving only the first lens group G1 in the optical axis direction.

An aberration diagram of the imaging lens shown in FIG. 29 is shown in FIG.
0, FIG. 31, and FIG. 30 shows the spherical aberration, astigmatism, and distortion when the shooting distance is Δ, FIG. 31 shows the case where the shooting distance is 0.5 m, and FIG. 32 shows the case where the shooting distance is 0.2 m. 30 to 32, it can be seen that various aberrations are well corrected even when the shooting distance changes.

The solid-state image sensor has a horizontal pixel of 1800 ×
It is possible to use a pixel having a vertical 1200, a pixel pitch of 4.2 μm for both horizontal and vertical, and each pixel arranged in a square.

The focus adjustment can be performed by moving the entire lens system with the air gap between the second lens 82 and the third lens 83 fixed at d ₄ = 2.21 mm. Can obtain an image with a good resolution over the entire screen when the shooting distance is in the range of ∞ to 0.5 m.

(Embodiment 9) FIG. 33 shows the structure of an imaging lens according to Embodiment 9 of the present invention.

The first lens 91 is composed of seven lenses.
And the second lens 92 are each a negative meniscus lens having a surface with a strong curvature facing the image side, the third lens 93 is a biconvex lens, the fourth lens 94 is a biconvex lens having an aspheric object side surface, and the fifth lens. The reference numeral 95 denotes a biconcave lens, the sixth lens 96 denotes a biconvex lens having an aspherical surface on the image side, and the seventh lens 97 denotes a positive meniscus lens having a surface with a strong curvature directed to the image side.

The first lens 91 and the second lens 92 form the first
The third lens 93 forms a second lens group G2, the fourth lens 94, the fifth lens 95 and the sixth lens 96 form a third lens group G3, and the seventh lens 97 forms a third lens group G3. A fourth lens group G4 is formed, and a stop 98 is arranged between the third lens group 93 and the fourth lens 94. A parallel plate element F equivalent to a filter and a cover glass is arranged on the image side of the fourth lens group G4, and a light receiving surface P of the solid-state imaging device is arranged on the image side.

The shooting distance of the imaging lens shown in FIG.
Table 9 shows lens data in the case of.

[0124]

[Table 9]

The focus adjustment when the photographing distance is changed is performed by fixing the lenses from the second lens group G2 to the image pickup device and moving only the first lens group G1 in the optical axis direction.

FIGS. 34, 35 and 36 show aberration diagrams of the imaging lens shown in FIG. 33 when the aperture is opened. 34 shows the case where the shooting distance is Δ, FIG. 35 shows the case where the shooting distance is 0.5 m, and FIG. 36 shows the case where the shooting distance is 0.2 m.
This is distortion. It can be seen from FIGS. 34 to 36 that various aberrations are favorably corrected even when the shooting distance changes.

As the solid-state imaging device, the number of pixels is 1800 × horizontal.
It is possible to use a pixel having a vertical 1200, a pixel pitch of 4.2 μm for both horizontal and vertical, and each pixel arranged in a square.

The focus adjustment can be performed by moving the entire lens system with the air gap between the second lens 92 and the third lens 93 fixed at d ₄ = 2.22 mm. Can obtain an image with a good resolution over the entire screen when the shooting distance is in the range of ∞ to 0.5 m.

(Embodiment 10) FIG. 37 shows a schematic configuration of an electronic still camera according to Embodiment 10 of the present invention as viewed from the side. In FIG. 37, 10
2 is an imaging lens, 103 is a solid-state imaging device, and 104 is a liquid crystal monitor.

An imaging lens 102 is disposed in front of the housing 101, and a solid-state imaging device 103 is disposed behind the imaging lens 102.
Are arranged, and a liquid crystal monitor 104 is arranged behind the housing 101. Solid-state image sensor 102 and liquid crystal monitor 104
And are in close proximity.

The solid-state image sensor 103 has an effective pixel number of horizontal
1800 × 1200 vertical, pixel pitch 4.2μm horizontal × 4.2μ vertical
m, the effective screen size is 7.56 mm (horizontal) × 5.04 mm (vertical), the diagonal length of the effective area is 9.086 mm, and a fine positive lens is provided for each pixel.

As the imaging lens 102, the imaging lens shown in FIG. 1 is used. 7. Constituting the imaging lens 102
Of the lenses, the first lens 11 and the second lens 12 are attached to the front lens barrel 105, and the remaining five lenses 1
3, 14, 15, 16, and 17 are attached to the rear barrel 106, the solid-state imaging device 103 is attached to the rear end of the rear barrel 106, and a filter 107 is arranged between the seventh lens 17 and the solid-state imaging device 103. Have been. A stop is arranged between the second lens 12 and the third lens 13 (not shown). The front barrel 105 is movable along two guide poles 108 (only one of the two is shown) parallel to the optical axis.

The filter 107 is formed by joining a first quartz plate, a second quartz plate, an infrared cut filter, and a third quartz plate with a transparent adhesive in order from the object side. The three quartz plates function as optical low-pass filters. The three quartz plates are parallel planes, and each optical axis is inclined by 45 ° with respect to the optical axis. The direction in which the optical axis of each quartz plate is projected on the light receiving surface of the solid-state image sensor 103 is the same as
When viewed from the 02 side, the first crystal plate is rotated 45 ° counterclockwise from the screen horizontal direction, the second crystal plate is rotated horizontally 45 ° from the screen, and the third crystal plate is rotated 45 ° clockwise from the horizontal direction of the screen. The direction is rotated. The infrared cut filter transmits the solid-state image sensor 10
The infrared light incident on the light receiving surface of No. 3 is removed to prevent the generation of an erroneous signal due to the infrared light. Further, the optical low-pass filter prevents generation of erroneous signals such as moiré caused by the pixel structure of the solid-state imaging device 103.

The front lens barrel 105 is moved by an actuator 112. By inputting a control signal to the actuator 112, the focus of the imaging lens can be adjusted. Automatic focus adjustment is performed by detecting a high-frequency component of an electric signal output from the solid-state imaging device 103 while slightly moving the front barrel 105 and determining the position of the front barrel 105 so that the high-frequency component is maximized. .

The electronic still camera shown in FIG. 37 adjusts the focus by moving the front lens barrel 105 in accordance with the change in the photographing distance, so that the whole screen has a wide photographing distance of ∞ to 0.2 m. , A good image can be obtained, and the depth can be reduced because the entire optical length of the imaging lens 102 is short.

Although the solid-state image sensor 103 is provided with a minute positive lens for each pixel, since the imaging lens 102 has good telecentricity, light passing through each minute positive lens can be efficiently transmitted to each pixel. Can be reached. Therefore, the light receiving sensitivity increases over the entire screen.

In the configuration shown in FIG. 37, the seventh lens 1
7, the filter 107 and the solid-state image sensor 103 do not move. Therefore, if the space from the seventh lens 17 to the solid-state image sensor 103 is made to be a closed structure, the light-receiving surface of the solid-state image sensor 103 from the image side surface of the seventh lens 17 Dust can be easily prevented from adhering to each surface of the solid-state imaging device 103.
The problem that a blurred image appears in the output signal from the device can be avoided.

In this manner, a compact electronic still camera having a high resolution over the entire screen over a wide range of photographing distance can be realized.

In the electronic still camera shown in FIG. 37, the imaging lens according to the second embodiment is used instead of the imaging lens according to the first embodiment.
The imaging lenses of Embodiments 6, 8, and 9 can also be used. Also, the solid-state imaging device 103
The effective pixel number is 1600 horizontal × 1200 vertical, the pixel pitch is 3.3 μm horizontal × 3.3 μm vertical, and the effective screen size is 5.
28mm x vertical 3.96mm, diagonal length of effective area is 6.600mm
In place of this, the imaging lens of Embodiment 7 can be used.

The optical system of the electronic still camera shown in FIG. 37 can be used for a video camera for moving images. In this case, not only a moving image but also a high-resolution still image can be shot.

(Embodiment 11) FIG. 38 shows a schematic configuration of the inside of a video camera according to Embodiment 11 of the present invention viewed from the side. In FIG. 38, 122 is an imaging lens, 123 is a solid-state imaging device, and 124 is a liquid crystal monitor.

In this video camera, similarly to the electronic still camera shown in FIG. 19, an imaging lens 122 is arranged on the front side of a housing 121, and a solid-state imaging device 123 is arranged on the rear side of the imaging lens 122. A liquid crystal monitor 124 is arranged on the rear side of 121, and a parallel flat glass plate 125 is arranged on the object side of the imaging lens 122. Glass plate 12
5 is fixed to the housing 121.

In the solid-state image sensor 123, the number of effective pixels is horizontal.
1800 × 1200 vertical, pixel pitch 4.2μm horizontal × 4.2μ vertical
m, the effective screen size is 7.56 mm (horizontal) × 5.04 mm (vertical), the diagonal length of the effective area is 9.086 mm, and a fine positive lens is provided for each pixel.

As the imaging lens 122, the imaging lens shown in FIG. 1 is used. As in the electronic still camera shown in FIG. 37, of the seven lenses constituting the imaging lens 122, the first lens 11 and the second lens 12 are the front lens barrel 1
26, and the remaining five lenses 13, 14,
15, 16, and 17 are attached to the lens barrel 127, the solid-state imaging device 123 is attached to the rear end of the rear lens barrel 127, and the filter 12 is disposed between the seventh lens 17 and the solid-state imaging device 123.
8 are arranged. Solid-state image sensor 123 and filter 1
28 is the solid-state imaging device 10 shown in FIG.
3. Same as the filter 107. The front lens barrel 126 is movable along two guide poles 129 parallel to the optical axis (only one of the two is shown).
Driven by 30.

In order to move the front lens barrel 126 at high speed for focus adjustment, the front lens barrel 126 and the lenses 11 and 12 are moved.
It is necessary to make the moving section composed of the lightest possible.
However, when the moving portion is lightened, the strength is weakened. When an external force is directly applied to the lenses 11 and 12, the front lens barrel 1 becomes weak.
The moving mechanism 26 and the actuator 130 are easily damaged. There is also a problem that dust easily flows into the inside of the imaging lens 122 from the gap. However, the glass plate 125
Is attached to the front part of the housing 121, it is possible to prevent the moving mechanism from being damaged by an external force, and to prevent dust from flowing into the imaging lens 122. Since the spread angle of the light emitted from an arbitrary point on the object and incident on the imaging lens is very small, even if a parallel flat glass plate is arranged on the object side of the imaging lens, the resolution does not deteriorate. .

As in the configuration shown in FIG. 37, it is easy to make the space from the seventh lens 17 to the solid-state image pickup device 123 a sealed structure, and the solid-state image pickup device 123 Can be easily prevented from adhering to the respective surfaces up to the light receiving surface, and the problem that an image blurred by the dust appears in the output signal from the solid-state imaging device 123 can be avoided.

In the video camera shown in FIG. 38, the front lens barrel 126 is moved in accordance with the change in the shooting distance to adjust the focus, so that the entire screen has a high resolution in the wide shooting range of ∞ to 0.2 m. Can be obtained, and the depth can be shortened because the entire optical length of the imaging lens 122 is short.

Although the solid-state image pickup device 103 is provided with a minute positive lens for each pixel, the same operation as that shown in FIG. 37 is obtained, so that the light receiving sensitivity is increased over the entire screen.

Although the video camera shown in FIG. 38 mainly shoots a moving image, it can also shoot a still image. In the case of a moving image, it is preferable to shoot with a smaller number of pixels than the solid-state imaging pixels, and in the case of a still image, it is preferable to shoot with the number of pixels of the solid-state imaging device.

In this way, a compact video camera having a high resolution over the entire screen over a wide range of shooting distance can be realized.

It should be noted that the video camera shown in FIG.
Instead of the imaging lens of the first embodiment, the imaging lenses of the second to sixth, eighth, and ninth embodiments can be used. Further, as the solid-state imaging device 123, the number of effective pixels is 1600 × 1200 horizontally, the pixel pitch is 3.3 μm × 3.3 μm, and the effective screen size is 5.28 m.
If it is replaced with a lens having a dimension of mx vertical 3.96 mm and a diagonal length of the effective area of 6.600 mm, the imaging lens of the seventh embodiment can be used.

If the video camera shown in FIG. 38 is dedicated to a still image, it becomes an electronic still camera.

[0153]

As described above, according to the present invention, it is possible to provide an imaging lens having a high resolution over the entire screen and a short overall optical length over a wide range of the photographing distance. Further, by using this imaging lens, a compact electronic still camera or video camera having a high resolution, a wide photographing distance range, and a compact size can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of an imaging lens according to a first embodiment of the present invention;

FIG. 2 is an aberration diagram when the imaging distance of the imaging lens in Embodiment 1 of the present invention is ∞.

FIG. 3 is an aberration diagram when an imaging distance of an imaging lens is 0.5 m in Embodiment 1 of the present invention.

FIG. 4 is an aberration diagram when the imaging distance of the imaging lens in Embodiment 1 of the present invention is 0.2 m.

FIG. 5 is a configuration diagram showing a configuration of an imaging lens according to Embodiment 2 of the present invention;

FIG. 6 is an aberration diagram when the imaging distance of the imaging lens in the second embodiment of the present invention is ∞.

FIG. 7 is an aberration diagram when the imaging distance of the imaging lens is 0.5 m in the second embodiment of the present invention.

FIG. 8 is an aberration diagram when the imaging distance of the imaging lens in Embodiment 2 of the present invention is 0.2 m.

FIG. 9 is a configuration diagram showing a configuration of an imaging lens according to Embodiment 3 of the present invention.

FIG. 10 is an aberration diagram when the imaging distance of the imaging lens in Embodiment 3 of the present invention is ∞.

FIG. 11 is an aberration diagram when an imaging distance of an imaging lens is 0.5 m in Embodiment 3 of the present invention.

FIG. 12 is an aberration diagram when the imaging distance of the imaging lens in Embodiment 3 of the present invention is 0.2 m.

FIG. 13 is a configuration diagram showing a configuration of an imaging lens according to Embodiment 4 of the present invention;

FIG. 14 is an aberration diagram when the imaging distance of the imaging lens is ∞ according to the fourth embodiment of the present invention.

FIG. 15 is an aberration diagram when the imaging distance of the imaging lens in Embodiment 4 of the present invention is 0.5 m.

FIG. 16 is an aberration diagram when the imaging distance of the imaging lens in Embodiment 4 of the present invention is 0.2 m.

FIG. 17 is a configuration diagram showing a configuration of an imaging lens according to a fifth embodiment of the present invention.

FIG. 18 is an aberration diagram when the imaging distance of the imaging lens is ∞ according to the fifth embodiment of the present invention.

FIG. 19 is an aberration diagram when the imaging distance of the imaging lens is 0.5 m in Embodiment 5 of the present invention.

FIG. 20 is an aberration diagram when the imaging distance of the imaging lens in Embodiment 5 of the present invention is 0.2 m.

FIG. 21 is a configuration diagram showing a configuration of an imaging lens according to a sixth embodiment of the present invention;

FIG. 22 is an aberration diagram when the imaging distance of the imaging lens in Embodiment 6 of the present invention is ∞.

FIG. 23 is an aberration diagram when the imaging distance of the imaging lens in Embodiment 6 of the present invention is 0.5 m.

FIG. 24 is an aberration diagram when the imaging distance of the imaging lens in Embodiment 6 of the present invention is 0.2 m.

FIG. 25 is a configuration diagram showing a configuration of an imaging lens according to a seventh embodiment of the present invention.

FIG. 26 is an aberrational diagram when the imaging distance of the imaging lens in the seventh embodiment of the present invention is ∞.

FIG. 27 is an aberration diagram when the imaging distance of the imaging lens in Embodiment 7 of the present invention is 0.5 m.

FIG. 28 is an aberration diagram when the imaging distance of the imaging lens in Embodiment 7 of the present invention is 0.2 m.

FIG. 29 is a configuration diagram showing a configuration of an imaging lens according to Embodiment 8 of the present invention;

FIG. 30 is an aberration diagram when the imaging distance of the imaging lens is ∞ in the eighth embodiment of the present invention.

FIG. 31 is an aberration diagram when the imaging distance of the imaging lens in Embodiment 8 of the present invention is 0.5 m.

FIG. 32 is an aberrational diagram when the imaging distance of the imaging lens in Embodiment 8 of the present invention is 0.2 m.

FIG. 33 is a configuration diagram showing a configuration of an imaging lens according to a ninth embodiment of the present invention;

FIG. 34 is an aberration diagram when the imaging distance of the imaging lens is ∞ in the ninth embodiment of the present invention.

FIG. 35 is an aberration diagram when the imaging distance of the imaging lens in Embodiment 9 of the present invention is 0.5 m.

FIG. 36 is an aberration diagram when the imaging distance of the imaging lens in Embodiment 9 of the present invention is 0.2 m.

FIG. 37 is a schematic configuration diagram of an electronic still camera according to Embodiment 10 of the present invention.

FIG. 38 is a schematic configuration diagram of a video camera according to Embodiment 11 of the present invention.

[Explanation of symbols]

 G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group 102, 122 Imaging lens 103, 123 Solid-state imaging device 104, 124 Liquid crystal monitor 107, 128 Filter 125 Glass plate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H087 KA03 LA03 MA06 PA06 PA07 PA17 PA18 PB07 PB08 QA02 QA07 QA17 QA22 QA25 QA32 QA34 QA37 QA41 QA45 QA46 RA05 RA12 RA13 RA32 RA42 RA44 5C022 AA13 AC42 AC54 AC66 AC78 AC01 EA04 FA01

Claims (25)

[Claims] 1. A first lens unit having a negative power, a second lens unit having a positive power, a third lens unit having a positive power, a fourth lens unit having a positive power, and the second lens are arranged in this order from the object side. A stop disposed between the group and the third lens group, the first lens group including a negative meniscus lens having a surface with a strong curvature directed to the image side in order from the object side, and a negative lens; The second lens group includes a biconvex lens, the third lens group includes, in order from the object side, a positive lens, a biconcave lens, and a positive lens having a surface with a strong curvature facing the image side, and the fourth lens group. Has a positive lens, at least the most image-side surface of the third lens group is an aspheric surface, and the combined focal length of the entire lens system when the shooting distance is ∞ is f, and the combined focal length of the first lens group is the f _G1, a composite focal length of the second lens group f _G2, the third lens The composite focal length of the group f _G3, the composite focal length of the fourth lens group as _{f G4, 0.8 <| f G1} | / f <1.2 ‥‥‥ (1) 1.3 <f G2 < 2.4 ‥‥‥ (2) 1.2 <f _G3 /f<2.3２(3) 1.6 <f _G4 /f<2.6‥‥‥ (4) Imaging lens. Further, assuming that the refractive index of the lens closest to the object side in the third lens group is n _A and the radius of curvature of the object side surface of the lens is r _A , 0.9 <r _A / f (n _A The imaging lens according to claim 1, wherein the following condition is satisfied: -1) <1.8 ‥‥‥ (5). 3. The imaging lens according to claim 1, wherein the surface of the third lens group closest to the object is an aspheric surface. 4. The imaging lens according to claim 1, wherein, of the at least three lenses constituting the third lens group, two lenses on the image side are cemented. 5. The imaging lens according to claim 1, wherein the fourth lens group is formed by joining a positive lens and a negative lens. 6. An air gap between a third lens group and the fourth lens group when a predetermined parallel plate element is disposed between the fourth lens group and the image plane, the distance between the diaphragm and the image is increased. The imaging lens according to any one of claims 1 to 5, wherein the imaging lens is the largest among air intervals existing up to the surface. 7. A first lens group having a negative power, a second lens group having a positive power, a third lens group having a positive power, a fourth lens group having a positive power, and the second lens are arranged in this order from the object side. An imaging lens comprising a stop disposed between a group and the third lens group, wherein focus adjustment is performed by moving the first lens group along an optical axis. 8. The first lens group includes a negative meniscus lens having a surface with a strong curvature directed to the image side in order from the object side and a negative lens, the second lens group includes a biconvex lens, and the third lens group includes A positive lens, a biconcave lens, and a positive lens having a surface with a strong curvature directed to the image side in order from the object side; the fourth lens group includes a positive lens; and at least the most image-side surface of the third lens group. Is an aspheric surface, and when the shooting distance is ∞, the combined focal length of the entire lens system is f, the combined focal length of the first lens group is f _G1 , the combined focal length of the second lens group is f _G2 ,
Assuming that the composite focal length of the third lens group is f _G3 and the composite focal length of the fourth lens group is f _G4 , 0.8 <| f _G1 | / f <1.2 (1) 1.3 _{<f G2 /f<2.4 ‥‥‥ (2)} 1.2 <f G3 /f<2.3 ‥‥‥ (3) 1.6 <f G4 /f<2.6 ‥‥‥ (4 9. The imaging lens according to claim 7, wherein each of the following conditions is satisfied. 9. Assuming that the refractive index of the lens closest to the object side of the third lens group is n _A and the radius of curvature of the object side surface of the lens is r _A , 0.9 <r _A / f (n The imaging lens according to claim 8, wherein the following condition is satisfied: _A- 1) <1.8. 10. The imaging lens according to claim 8, wherein the surface of the third lens group closest to the object is an aspheric surface. 11. The image-side two lenses of at least three lenses constituting the third lens group are cemented.
The imaging lens according to claim 1. 12. The imaging lens according to claim 8, wherein the fourth lens group is formed by cementing a positive lens and a negative lens. 13. The third lens unit and the fourth lens unit in a state where a predetermined parallel plate element is disposed between the fourth lens unit and the image plane.
The imaging lens according to any one of claims 8 to 12, wherein an air gap between the lens group and the lens group is the largest among air gaps existing between the stop and the image plane. 14. An image pickup apparatus comprising: an imaging lens; and a solid-state imaging device.
An electronic still camera, wherein the imaging lens is the imaging lens according to any one of claims 1 to 6. 15. The electronic still camera according to claim 14, wherein the solid-state imaging device has a minute positive lens for each pixel. 16. An image pickup device comprising: a solid-state imaging device; and an imaging lens.
An electronic still camera, wherein the imaging lens is the imaging lens according to any one of claims 7 to 13. 17. The electronic still camera according to claim 16, wherein the solid-state imaging device has a minute positive lens for each pixel. 18. The electronic still camera according to claim 16, wherein a space between the lens closest to the image side of the imaging lens and the light receiving surface of the solid-state imaging device has a sealed structure. 19. The electronic still camera according to claim 16, further comprising a transparent plate having a plane parallel to the object side of the imaging lens. 20. An image pickup apparatus comprising: an imaging lens; and a solid-state imaging device.
A video camera, wherein the imaging lens is the imaging lens according to any one of claims 1 to 6. 21. The video camera according to claim 20, wherein the solid-state imaging device has a minute positive lens for each pixel. 22. An image pickup apparatus comprising: an imaging lens; and a solid-state imaging device.
A video camera, wherein the imaging lens is the imaging lens according to any one of claims 7 to 13. 23. The video camera according to claim 22, wherein the solid-state imaging device has a minute positive lens for each pixel. 24. The video camera according to claim 22, wherein a space between the lens closest to the image side of the imaging lens and the light receiving surface of the solid-state imaging device has a sealed structure. 25. The video camera according to claim 22, further comprising a transparent plate having a plane parallel to the object side of the imaging lens.